Photovoltaic devices such as solar cells are capable of converting solar radiation into useable electrical energy. The energy conversion occurs as the result of what is well known in the solar cell field as the "photovoltaic effect". Two basic steps are involved in the photovoltaic effect. Initially, solar radiation absorbed by the semiconductor generates electrons and holes. Secondly, the electrons and holes are separated by a built-in electric field in the semiconductor solar cell. This separation of electrons and holes results in the generation of an electrical current. A built-in electric field can be generated in a solar cell by, for example, a Schottky barrier. The electrons generated at the metal (Schottky barrier) semiconductor body junction flow toward the semiconductor body where said electrons can be collected.
PIN amorphous silicon solar cells generated higher open circuit voltages than Schottky barrier amorphous silicon solar cells; however, the short-circuit currents generated in PIN cells are lower than in Schottky barrier cells because of losses from the recombination of holes and electrons. The lower voltages of the Schottky barrier hydrogenated amorphous silicon solar cells are due mainly to the barrier height of the high work function metals being limited by surface states.
Thus, it would be highly desirable to increase the open circuit voltage of a Schottky barrier hydrogenated amorphous silicon solar cell and to also maintain a large value for the short-circuit current density.